Stainless Steel CB6
UNS J91804 · ASTM A743 Gr. CB6
CB6 (UNS J91804, ASTM A743 Gr.
Reference datasheet — CB6 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the N+T condition
CB6 tempers and conditions
CB6 is supplied in 6 conditions, soft to hard. N+T is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for heavy machining, straightening or welding repair before final hardening. | 400 | 620 | 24 | 180 HB | — |
Stress relieved | Condition of weld-repaired castings after mandatory post-weld temper; properties approach N+T with slightly lower local ductility. | 530 | 740 | 14 | 22 HRC | 2.9 % IACS |
N+TDefault Normalized and tempered | Standard supply condition for valve and pump castings: balanced strength, toughness and corrosion resistance. | 550 | 760 | 16 | 21 HRC | — |
As fabricated | Raw casting before heat treatment; hard, brittle untempered martensite — not for service, only for intermediate handling/machining allowance planning. | 650 | 900 | 5 | 36 HRC | 2.7 % IACS |
Hardened and tempered at ~590 °C | Choose when higher yield strength is needed and impact demands are moderate (shafts, stems, wear rings). | 700 | 900 | 13 | 28 HRC | — |
Hardened and low-temperature tempered ~230–280 °C | Maximum hardness/wear resistance condition; accept low toughness and reduced stress-corrosion tolerance. | 900 | 1,150 | 8 | 39 HRC | — |
What is CB6?
CB6 (UNS J91804, ASTM A743 Gr. CB6) is a 16% chromium cast martensitic stainless steel that retains martensitic hardenability while resisting corrosion better than CA15 and CA40. Sand and investment castings are supplied annealed, normalised-and-tempered, quenched-and-tempered or stress-relieved, giving about 550 MPa yield, 760 MPa tensile, 16% elongation and 230 HB (21 HRC), with service to 620 °C. Machinability is modest (score 45) and welding requires 200–300 °C preheat plus a mandatory post-weld temper; where weld repair dominates, low-carbon CA6NM (1.4317) is the usual alternative. CB6 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F). CB6 has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 83% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi).
What is CB6 used for?
- Valve trim
- Pump components
- Corrosion-resistant structural castings
Advantages
- Conducts heat well — 25 W/m·K (14.4 BTU/hr·ft·°F), better than 93% of stainless steel grades
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
- Easy to machine — 45/100, better than 84% of stainless steel grades
- High strength — 550 MPa (79.8 ksi), better than 83% of stainless steel grades
- Low embodied carbon — 3.6 kg CO₂/kg, better than 83% of stainless steel grades
Limitations
- Limited formability — 12/100, worse than 93% of stainless steel grades
- Limited ductility — 16%, worse than 88% of stainless steel grades
- Difficult to weld — 35/100, worse than 86% of stainless steel grades
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 85% of stainless steel grades
CB6 properties
Typical room-temperature values for CB6-N+T; bars are the position among stainless steel grades.
Physical3
CB6 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
CB6 has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 83% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
CB6 is rated for continuous service to 620°C (1,148 °F). It conducts heat at 25 W/m·K (14.4 BTU/hr·ft·°F), better than 93% of stainless steel grades. Thermal expansion is 10.4 µm/m·K (5.78 µin/in·°F).
Electrical3
CB6 conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of CB6 takes about 53 MJ of energy and emits 3.6 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 75%.
Manufacturability8
CB6's machinability is fair (45/100, better than 84% of stainless steel grades); weldability fair (35/100); formability not recommended (12/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. CB6 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with CB6
Is CB6 easy to machine?
Machine in the annealed or high-tempered condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed to avoid work hardening and glazing; above 30 HRC prefer grinding or CBN.
Can CB6 be welded?
Weldable with matching 410NiMo/E410NiMo or austenitic 309L filler, but requires 200–300 °C preheat, controlled interpass and a mandatory post-weld temper to avoid martensite cracking.
Can CB6 be formed, bent or molded?
Sand or investment cast; needs generous risering (long freezing range, ~2% solidification shrinkage) and slow, protected cooling to limit hot tearing and quench cracks.
CB6 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Clow-carbon martensitic; verify limit against current ASTM A743 edition | ≤ 0.06 | 0.04 |
| Mn | ≤ 1 | 0.6 |
| Si | ≤ 1 | 0.7 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Cr16% Cr class — higher than CA-15/CA-40 | 15.5 – 17.5 | 16.5 |
| Nipresent to stabilise austenite/martensite at low carbon | ≤ 2.5 | 1.6 |
| Mooptional/residual | ≤ 0.75 | 0.35 |
| Fe | balance |
What surface finishes work on CB6?
Passivate per ASTM A967 after machining; takes a good mechanical or electropolish; hard chrome or nitriding can be used for wear surfaces — do not anodize.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel CB6 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- J91804
- ASTM
- A743 Gr. CB6
How much does CB6 cost?
CB6 is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
CB6 — frequently asked
What is CB6 used for?
CB6 is typically used for valve trim, pump components and corrosion-resistant structural castings. In short: more corrosion-resistant than CA15; hardenable cast martensitic; 620 °C service limit.
What is the yield strength of CB6?
CB6 has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 83% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is CB6 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 84% of stainless steel grades). Machine in the annealed or high-tempered condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed to avoid work hardening and glazing; above 30 HRC prefer grinding or CBN.
Can CB6 be welded?
With care — weldability is rated fair (35/100). Weldable with matching 410NiMo/E410NiMo or austenitic 309L filler, but requires 200–300 °C preheat, controlled interpass and a mandatory post-weld temper to avoid martensite cracking.
What surface finishes work on CB6?
Passivate per ASTM A967 after machining; takes a good mechanical or electropolish; hard chrome or nitriding can be used for wear surfaces — do not anodize.
Can CB6 be formed, bent or molded?
Sand or investment cast; needs generous risering (long freezing range, ~2% solidification shrinkage) and slow, protected cooling to limit hot tearing and quench cracks.
What is the maximum service temperature of CB6?
CB6 is rated for continuous use to about 620°C (1,148 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CB6 N+T and CB6-A?
N+T is the default condition — standard supply condition for valve and pump castings: balanced strength, toughness and corrosion resistance. A: softest condition for heavy machining, straightening or welding repair before final hardening. Yield strength is 550 MPa in N+T versus 400 MPa in A.
How much does CB6 cost?
CB6 is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2019)
- ASTM A487/A487M — Steel Castings Suitable for Pressure Service — ASTM International (2020)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- UNS J91804 alloy record (Metals & Alloys in the Unified Numbering System) — SAE/ASTM (2017)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.